High surface area dual promoted iron/managanese spinel compositions

ABSTRACT

Slurried, high surface area, Cu and Group IA or IIA dual metal promoted Mn-Fe spinels which are fully reduced and carburized provide exceptionally high catalytic activity and selectivity in the conversion ofCo/H 2  to alpha-olefins, particularly when reduced and carbided in-situ. These copper and Group IA or IIA metal promoted iron-manganese catalysts maintain good activity and selectively under low pressure reaction conditions.

This application is a continuation-in-part of copending U.S. Ser. No.564,465 filed on Dec. 20, 1983.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to new, dual promoted, high surface area,iron/manganese spinel compositions promoted with copper and with a GroupIA or Group IIA metal, the preparation and use. More particularly, thisinvention relates to new, unsupported, single phase Fe-Mn spinelcompositions dual promoted with copper and a Group IA or Group IIAmetal, their preparation and use as catalysts in Fischer-Tropsch slurryprocesses for producing alpha olefins from mixtures of CO and H₂. Thesecatalysts have a surface area greater than about 30 M² /g in which theatomic ratio of Fe to Mn is greater than 2:1.

2. Background of the Disclosure

Fischer-Tropsch processes have long been known to produce gaseous andliquid hydrocarbons containing C₂ -C₄ olefins. Because of the importanceof C₂ -C₄ olefins, particularly as feedstocks for the chemical industry,modifications of the Fischer-Tropsch process are constantly beingpursued toward the goals of maximizing C₂ -C₄ olefin selectivity withthe particular objective of maintaining high catalyst activity andstability under the reaction conditions. The main thrust of the effortsin this area has been in the area of catalyst formulation.

Coprecipitated and/or supported iron-based catalysts, including thosecontaining manganese, are known for producing C₂ -C₃ olefins. Examplesof disclosures in the art directed to such iron-manganese catalystsand/or alloys include: W. L. vanDijk, et al., Appl. Catal., 2, 273(1982); Eur. Pat. Appl. 49888 to Ruhrchemie (1981); H. J. Lehman, 73rdAICHe Meeting Paper #103D; W. D. Deckwer, et al., Chem. Ing. Tech., 53(10), 818 (1981); V. Rao and R. Gormley, Hydrocarbon Processing, 139,November (1981); H. Kolbel and K. Tillmetz, U.S. Pat. No. 4,177,203(1970); EPO Patent Publication No. 0,071,770; U.S. Pat. No. 2,605,275;U.S. Pat. No. 2,850,515; Prepr. Div. Pet. Chem. Am. Chem. Soc. (1978)23(2) pp 513-20; Intersoc. Energy Convers. Eng. Conf. 1978, 13(1) pp482-6; U.S. Pat. No. 4,186,112; EP No. 49,888; React. Kinet. Catal.Lett. 1982, 20( 1-2) pp 175-80; U.S. Pat. No. 2,778,845; Khim. (1)Tekhnol. Topliv i Masel (Russ.) 10(6) 5-10 (1965); UK Patent Appln. No.2,050,859 A; German Patent Appln. DT No. 2919-921; Prace Ustavu VyzkumPaliv 8, p. 39-81 (1964) (Czech).

An iron-manganese spinel of the formula, Fe₂ MnO₄, is reported as acatalyst component formed during Fischer-Tropsch synthesis in which acoprecipitated Fe/Mn oxide catalyst is initially employed in AppliedCatalysis 5 (1983) pp. 151-170.

U.S. Pat. No. 2,778,845 to McGrath, et al. discloses a non-spinel type,low surface area, sintered catalyst composition containing reduced ormetallic iron as a major component. These compositions are used tosynthesize hydrocarbons from mixtures of hydrogen and and carbonmonoxide and are formed via a high temperature fusion in an electric arcfurnace. The sintered or fused composition must then be reduced,preferably in hydrogen, to form the metallic iron-containing catalyst.U.S. Pat. No. 2,605,275 to Kearby, et al. discloses forming hydrocarbonsfrom mixtures of CO and H₂ employing low surface area, sintered, spineltype catalysts containing iron and a divalent metal of the generalformula Fe₂ MeO₄ wherein Me is the divalent metal. The molar ratio of Meto Fe₂ O₃ is preferably greater than 1:1. Thus, the ratio of Fe/Me is nogreater than 2/1 and preferably less than 2/1.

U.S. Pat. No. 3,970,738 to Matsui, et al. discloses an iron oxidecomposition containing a minor amount of manganese oxide and a processfor making same. The object of the invention in this disclosure isstated as being able to provide iron oxide products substantially freefrom manganese compounds as impurities. The upper limit on the manganesecomponent of these iron oxide products is taught and claimed as beingless than 0.2 weight percent calculated as MnO. Maiti, et al. in"Iron/Manganese Oxide Catalysts for Fischer-Tropsch Synthesis. Part I:Structural and Textural Changes by Calcination, Reduction andSynthesis", J. Applied Catalysis, v5, p. 151-170 (1983) discloses theuse of iron-manganese containing catalysts in a Fischer-Tropsch processto produce olefins. Spinel compositions are suggested as being presentin the catalysts used in this reference. This reference does notdisclose the use of copper and potassium promoted spinels.

Van Dijk, et al. in "Effects of Manganese Oxide and Sulfate on theOlefin Selectivity of Iron Catalysts in the Fischer Tropsch Reaction",J. Applied Catalysis, v2, p. 273-288 (1982) disclose a Fischer-Tropschcatalyst which, on page 277, is set forth as a mixture of alpha ironoxide, alpha iron hydroxide and Mn₂ O₃. This reference discloses thatthese catalysts produce substantially more than about 20% methane makeand an equilibrium methane selectivity (on page 283) of over 30%. U.S.Pat. No. 4,177,203 to Kolbel, et al. discloses, in line 6-9 of column 3,a Fischer-Tropsch process using a catalyst which contains more than 50%manganese and less than 50% iron. This process produces low molecularweight olefins. Kolbel, et al. in "Feedstock For Chemical Industry BySelective Fischer-Tropsch-Synthese", 1978 Society of AutomotiveEngineers, p. 482-486, disclose a Fischer-Tropsch catalyst consisting ofa precipitated mixture of gamma Mn₂ O₃ and alpha Fe₂ O₃ inserted in themanganese oxide lattice. Thus, the catalyst composition of thisreference consists of mixed oxide phases. Further, the ratio ofmanganese to iron oxide of the catalyst disclosed therein is set forthas being between 8 and 10.

Europan Pat. No. 71,770 discloses iron-manganese catalysts promoted withpotassium, wherein the maximum ratio of iron to manganese is 1:2.Compositions set forth in the Tables on pages 11 and 13 of thisreference disclose iron/manganese ratios of 1:3.

Bruce, et al. in "Light Olefin Production from CO/H₂ Over SilicaSupported Fe/Mn/K Catalysts Derived From a Bimetallic Carbonyl Anion,[Fe₂ Mn(CO)₁₂ ]", React. Kinet. Catal. Lett., v. 20, Nos. 1-2, p.175-180 (1982) disclose olefin production using supported catalystsprepared from carbonyl precursors, with silica being the support.Methane selectivity incurred with the use of this catalyst inFischer-Tropsch hydrocarbon synthesis reactions is disclosed as about31% (unpromoted) and 18% (potassium promoted).

Jenson, et al. in "Studies on Iron-Manganese Oxide Carbon MonoxideCatalysts; I. Structure of Reduced Catalyst", J. of Catalysts, v. 92, p.98-108 (1985) disclose iron-manganese catalysts showing enhancedselectivity for low molecular weight olefins from synthesis gas. Thereduced catalyst composition is disclosed as having been found to be analpha iron oxide and a manganese (II oxide) as separate phases, with themanganese oxide phase containing some divalent iron oxide in solidsolution. Maiti, et al. in "Iron/Manganese Oxide Catalysts ForFischer-Tropsch Synthesis. Part II, Crystal Phase Composition, Activityand Selectivity" J. Appl. Catal. 16 (2) 215-25 (1985) disclosestructural changes in the Fe-Mn oxide system under synthesis gases as afunction of various pretreatments.

French Pat. No. 2,554,433 discloses passing a mixture of H₂ and CO overa spinel catalyst having the general formula of Li_(x) Cu_(1-x) Fe₅ O₈and French Pat. No. 2,553,399 discloses a similar process employing acatalyst having the general formula of Cu_(x) Mn_(1-x) Fe_(y) Cr_(1-y)O₄.

Finally, Pennline, et al. in "The Effect of Activation and Promotion ona Fischer-Tropsch Catalyst" 189th ACS National Meeting (Miami Beach4/28-5/3/85) ACS Div. Fuel Chem. Prep. 30# 3:310-17 (1985) disclose aFischer-Tropsch catalyst employed in a slurry reactor employingcatalysts containing 21% iron 79% manganese oxide activated in-situ,under various conditions.

However, none of the references cited above describe a Fisher-Tropschhydrocarbon process employing an unsupported single phase Fe/Mn spinelcatalyst having an Fe:Mn atomic ratio above 2:1 and a surface areagreater than about 30 M² /g and being dual promoted with both copper anda Group IA or IIA metal promoter agent.

SUMMARY OF THE INVENTION

The present invention relates to relatively high surface area,unsupported, single phase, iron-manganese spinels which are dualpromoted with both copper and a Group IA or IIA metal useful forsynthesizing alpha olefins from mixtures of CO and H₂ in a slurryprocess, said spinels having the empirical formula:

    Fe.sub.x Mn.sub.y O.sub.4

wherein x and y are integer or decimal values, other than zero, with theproviso that the sum of x+y is 3 and the ratio of x/y is above 2:1,wherein said spinel exhibits a powder X-ray diffraction patternsubstantially isostructural with Fe₃ O₄, with said promoter metals beingsubstantially deposited on the surface of said spinel and said surfacearea of said spinel being greater than about 30 M² /g.

These catalyst compositions provide greater catalytic activity and alsogreater selectivity towards alpha olefins than similar compositions suchas the relatively low surface area iron-manganese spinels, not promotedwith copper, which are disclosed in co-pending U.S. patent applicationSer. Nos. 564,464 and 564,464 filed on Dec. 20, 1983. Further, thecatalyst compositions of this invention are active both in fixed bed andin slurry hydrocarbon synthesis processes, compared to the catalysts ofsaid co-pending applications which are substantially inactive in slurryprocesses.

The high surface area catalyst compositions of this invention can beprepared by a process of adding an alpha-hydroxy aliphatic carboxylicacid, e.g., glycolic acid, to an acidic aqueous solution containingdissolved iron and cobalt salts and subsequently evaporating thesolution to dryness to yield an amorphous, mixed metal glycolate, which,on calcining at elevated temperature, forms a mixed metal oxideexhibiting a spinel crystal structure and possessing a high surfacearea. The unsupported, high surface area Mn-Fe spinels prepared in thismanner possess BET surface areas greater than 30 M² /g. Typically thespinels of this invention will have surface areas ranging between about50-200 M² /g.

The so-formed mixed metal oxide or spinel is then converted to thecatalyst by contacting, at elevated temperature, with a mixture of H₂and CO to form the reduced-carbided catalyst. Preferably the reductionand carbiding is accomplished in-situ in a slurry bed.

The spinels prepared according to the process of this invention may bepromoted by surface impregnation or deposition with Group IA or GroupIIA and copper metal salts prior to the reduction and carbiding step.

DETAILED DESCRIPTION OF THE INVENTION

The unsupported, high surface area, copper and alkali- or alkaline earthmetal salt promoted iron-manganese single phase spinels of thisinvention are new compositions of matter which are isostructural withFe₃ O₄, as determined by X-ray diffractometry using copper K alpharadiation and exhibit a single spinel phase. By the term "spinel" ismeant a crystal structure whose general stoichiometry corresponds to AB₂O₄, where A and B can be the same or different cations. Included withinthis definition is the commonly found spinel, MgAl₂ O₄, A and B can havethe following cationic charge combinations: A=+2, B=30 3, A=+4, B=+2, orA=+6, B=30 1. Spinels contain an approximately cubic close-packedarrangement of oxygen atoms with 1/8th of the available tetrahedralinterstices and 1/2 of the octahedral interstices filled, and canexhibit hundreds of different phases. Further description of the spinelstructure can be found in "Structural Inorganic Chemistry" by A. F.Wells, Third Edition, Oxford Press, and the Article "Crystal Chemistryand Some Magnetic Properties of Mixed Metal Oxides with the SpinelStructure" by G. Blasse, Phillips Research Review Supplement, Volume 3,pp 1-30, (1964). By the term "isostructural" is meant crystallizing inthe same general structure type such that the arrangement of the atomsremains very similar with only minor change in unit cell constants, bondenergies and angles. By the term "single phase spinel", as used herein,is meant one structural and compositional formula, corresponding to asingle spinel material into which all of the metal components areincorporated, and exhibiting one characteristic X-ray diffractionpattern.

The copper and Group IA or Group IIA metal promoted iron-manganesespinels of this invention possesses a BET surface area of over 30 M² /gand typically of from about 50-100 M² /g with about 100 M² /g being ageneral average surface area, as determined by the well-known BETsurface area measurement technique as described in the reference JACS60, p. 309 (1938) by S. Brunauer, P. H. Emmett, and G. Teller. Thisrange of surface area generally corresponds to a particle size range ofabout 100 to 200 angstroms.

The spinel can be represented by the formula: Fe_(x) Mn_(y) O₄, whereinx and y are decimal or integer values, other than zero, and wherein thesum of x plus y is 3, and the ratio of x to y is greater than 2:1,preferably being from above 2:1 to about 19:1. Particularly preferred iswhere the iron to manganese atomic ratio is about 3:1 to 7:1. Thecomposition can further be comprised of a mixture of single phasespinels, of different iron-manganese atomic ratios.

Representative examples of the various spinels corresponding to theformula are Fe₂.85 Mn₀.15 O₄, Fe₂.625 Mn₀.375 O₄, Fe₂.25 Mn₀.75 O₄. Adual promoted spinel composition of the subject invention which is setforth in the Examples below is Fe₂.25 Mn₀.75 O₄ /2% K, 1% Cu.

In general, the physical properties of the subject spinels of thisinvention are similar to those of magnetite and include melting point ofabove 1400° C., and a color of brownish-red. The dual promoted,iron-manganese spinels of this invention are used in unsupported for inH₂ /CO hydrocarbon synthesis.

Representative examples of suitable classes of the copper and Group IAand IIA metal promoter agents include carbonates, bicarbonates, organicacid and inorganic acid salts e.g. acetates, nitrates, halides, andhydroxide salts of copper and Group IA and IIA metals including lithium,sodium, potassium, cesium, rubidium, barium, strontium, magnesium andthe like. The use of sulfate salts of the promoter metal should beavoided, because it has been found that the resulting catalyst will beinactive in the slurry process.

Representative examples of specific promoter agents include coppercarbonate, copper bicarbonate, copper nitrate, potassium carbonate,potassium bicarbonate, cesium chloride, rubidium nitrate, lithiumacetate, potassium hydroxide, and the like. Group IA compounds arepreferred with the copper with potassium being particularly preferred.The Group IA and IIA promoters will be present in an amount of fromabout a 0.1 to 10 gram-atom % of the total gram-atoms of metals present.A preferred level of promoter agent is in the range of 1 to 2 gram-atom% of the total gram-atom metal present. In the empirical formulas usedherein, the amount of the promoter agent, e.g., potassium, is expressedin terms of gram atom percent based on the total gram-atoms of metalused. Thus, "1 gram-atom percent of potassium signifies the presence of1 gram-atom of potassium per 100 total gram atoms of combined gram atomsof Fe and Mn. Thus, the symbol "/1% K" as used herein indicates 1gram-atom percent potassium based on each 100 gram atom of the totalgram atom of iron and manganese present.

The copper promoter metal will be present in the catalyst in an amountof from about 0.1 to 2.0 gram-atom percent based on the total metalcontent of the final catalyst composition and preferably from about 0.5to 1.5 gram-atom percent.

The utility of these spinels is their ability upon subsequentreduction-carbiding, preferably in-situ in a slurry bed, to form activecatalysts useful for making C₂ -C₂₀ olefins from CO/hydrogen in aFischer-Tropsch slurry process.

The reduced-carbided forms of the above-described spinel are alsosubjects of this invention.

The copper and Group IA or IIA metal promoted spinels undergounexpectedly facile in-situ reduction in a slurry liquid andpretreatment to form copper and Group IA or IIA metal promotediron-manganese spinels in reduced form, which are further in-situcarbided to form slurry catalysts active in a Fischer-Tropsch slurryprocess for making C₂ -C₂₀ olefins from CO/hydrogen.

The spinels can be made by a process in which an aqueous solution ofmanganese and iron salts of an alpha-hydroxy aliphatic carboxylic acid,is evaporated to dryness, leaving an amorphous residue, which is thenheated at elevated temperature to substantially form the spinel, as asingle spinel phase, being isostructural with Fe₃ O₄ and possessing asurface area greater than 3 M² /g, preferably above 50 M² /g. Theheating is conducted such that no significant loss in surface area ofthe final spinel is incurred.

The key to the synthesis of these high surface area spinels is in theuse of an organic, saturated, aliphatic, alpha-hydroxy carboxylic acidto form a complex salt, which is soluble in the aforementioned aqueousmedium, at a pH on the acidic side, i.e., pH of 5-7. The solubility ofthe iron and manganese organic salts of the alpha-hydroxy carboxylicacid prevent crystallization from occurring, which would result in acrystalline product being obtained from the solution, that would possessa relatively low surface area.

This method of preparation utilizes an alpha-hydroxy aliphaticcarboxylic acid which acts as a solubilizing agent for the iron andcobalt salts in the aqueous solution. Any saturated aliphaticalpha-hydroxy carboxylic acid, containing at least one alpha-hydroxygrouping, can be used to form the soluble iron and manganese salts inthe subject invention process in aqueous solution, is deemed to beincluded within the scope of this invention. Representative examples ofsuch acids which can be mono-hydroxy or di-hydroxy or mono-carboxylic ordi-carboxylic are glycolic, malic, glyceric, mandelic, tartaric, lacticacids and mixtures thereof. A preferred carboxylic acid used in theprocess is glycolic acid.

The amount of acid used is at least the stoichiometric amount, i.e., 1to 1 molar ratio for each metal present and preferably in about a 5-10%molar excess of the stoichiometric amount. Higher ratios can be used, ifit is economical to do so. Lower amounts can also be used but wouldresult in incomplete iron and cobalt acid salt formation.

The first step in the process comprises forming an aqueous solution bydissolving iron salts and manganese salts, in a water-soluble salt formsuch as their nitrates, sulfates, chlorides, acetates, and the like, inwater.

The concentration of the salts in the aqueous liquid is not critical tothe extent that the salts are present in less than a saturated solutionto avoid precipitation. For example, an 80-90% saturated solution, ofcombined dissolved metal molarities for avoiding precipitation in theprocess, can be effectively used.

The temperature of the aqueous solution is not critical and may be aboveroom temperature to aid in the solubilizing process. However, roomtemperature is adequate and is the temperature generally used in theprocess. The pressure also is not critical in the process andatmospheric pressure is generally used.

The aqueous solution can also contain a small amount of organic solventsuch as ethanol, acetone, and the like for aiding in the solubilizing ofthe iron and manganese salts of the alpha-hydroxy carboxylic acid.

Following the dissolving of the iron and manganese salts, thealpha-hydroxy carboxylic acid is added, together with a sufficientquantity of base, usually being ammonium hydroxide, sodium hydroxide,potassium hydroxide, and the like, preferably ammonium hydroxide, tosolubilizing the resulting acid salts. The amount of base added issufficient to keep the pH in the range of about 5 to 7.0.

It should be noted that the exact sequence of steps need not be adheredto as described above, with the proviso that the resulting aqueoussolution contain dissolved iron and manganese salts in stoichiometricamounts as iron and manganese salts of alpha-hydroxy carboxylic acid insolution. If there are any insoluble materials present after addition ofthe base and organic acid, they should be filtered prior to theevaporation step.

At this point, the resulting solution is evaporated, as for example, byair drying, or under reduced pressure, at elevated temperature, aspracticed in a rotary evaporator, or in a vacuum drying oven.

The resulting material from the evaporation step is an amorphousresidue, generally being a powder. This residue is heated at elevatedtemperature at 100° to 350° C. preferably 100°-200° C. and still morepreferably 150°-200° C. for about 1 to 24 hours in generally air toresult in a substantially single spinel phase which is isostructuralwith Fe₃ O₄, as determined by X-ray diffractrometry, as previouslydescribed herein. Preferred temperature range is 100°-400° C., andparticularly preferred is about 350° C. for single phase spinelformation.

The dual promoted spinel is then reduced and carbided to form thecatalyst. This reduction and carbiding is done by contacting the dualpromoted spinel, at elevated temperature, with a suitable reactant suchas CO, CO/H₂, aliphatic or aromatic hydrocarbons, and the like.Preferably the reduction and carbiding is accomplished simultaneouslywith a mixture of CO/H₂ with a CO/H₂ molar ratio of from about 1:10 to10:1. A ratio of 1:2 has been found to be convenient in the laboratory.Still more preferably this reduction and carbiding will be accomplishedin-situ in a slurry liquid in a reactor.

The reduction-carbiding step is generally conducted at a temperature ofabout 250° C., or above and preferably at 300° to 400° C. and still morepreferably 270°-290° C. A preferred method of reducing and carbiding thecatalyst is in-situ in the slurry liquid to be used in theFischer-Tropsch process. A particularly preferred method is where thepromoted spinel is treated with a mixture of CO/hydrogen and reduced andcarbided in-situ in one step prior to hydrocarbon synthesis. Thepressure is generally about 1 atmosphere, and a space velocity of about20-20,000 v/v/hr is chosen in order to completely carbide the ironpresent in the spinel.

The resulting carbide is an active slurry catalyst for producing C₂ -C₂₀olefins in the described Fischer-Tropsch slurry process.

Also, a subject of the instant invention is a Fischer-Tropsch processfor producing C₂ -C₂₀ olefins by utilizing the Group IA or IIA metal andcopper promoted iron-manganese spinel, and the reduced, carbided, GroupIA or IIA metal and copper promoted iron-manganese spinel catalystdescribed hereinabove.

Although a fixed bed process can be used, a preferred process mode foroperating the Fischer-Tropsch process utilizing the catalysts describedherein is a slurry-type process wherein the catalyst in fine particlesize and high surface area being above 30 M² /g is suspended in a liquidhydrocarbon and the CO/hydrogen mixture forced through the catalystslurry allowing good contact between the CO/hydrogen and the catalyst toinitiate and maintain the hydrocarbon synthesis process.

Advantages of a slurry process over that of a fixed bed process are thatthere is better control of the exothermic heat produced in theFischer-Tropsch process during the reaction and that better control overcatalyst activity maintainance by allowing continuous recycle, recovery,and rejuvenation procedures to be implemented. The slurry process can beoperated in a batch or in a continuous cycle, and in the continuouscycle, the entire slurry can be circulated in the system allowing forbetter control of the primary products residence time in the reactionzone.

The slurry liquid used in the slurry process must be liquid at thereaction temperature, must be chemically inert under the reactionconditions and must be a relatively good solvent for CO/hydrogen andpossess good slurrying and dispersing properties for the finely dividedcatalyst. Representative classes of organic liquid which can be utilizedare high boiling paraffins, aromatic hydrocarbons, ethers, amines, ormixtures thereof. The high boiling paraffins include C₁₀ -C₅₀ linear orbranched paraffinic hydrocarbons; the aromatic hydrocarbons include C₂-C₂₀ single ring and multi- and fused ring aromatic hydrocarbons; theethers include aromatic ethers and substituted aromatic ethers where theether oxygen is sterically hindered from being hydrogenated; the aminesinclude long chain amines which can be primary, secondary, and tertiaryamines, wherein primary amines preferably contain at least a C₁₂ alkylgroup in length, secondary amines preferably contain at least two alkylgroups being C₇ or greater in length, and tertiary amines preferablycontain at least three alkyl groups being C₆ or higher in length. Theslurry liquid can contain N and O in the molecular structure but not S,P, As or Sb, since these are poisons in the slurry process.Representative examples of specific liquid slurry solvents useful aredodecane, tetradecane, hexadecane, octadecane, cosane, tetracosane,octacosane, dotriacontane, hexatriacontane, tetracontane,tetratetracontane, toluene, o-, m-, and p-xylene, mesitylene, C₁ -C₁₂mono- and multi-alkyl substituted benzenes, dodecylbenzene, naphthalene,anthracene, biphenyl, diphenylether, dodecylamine, dinonylamine,trioctylamine, and the like. Preferred liquid hydrocarbon slurry solventis octacosane or hexadecane.

The amount of catalyst used in the liquid hydrocarbon slurry solvent isgenerally about 1 to 100 g. of dry catalyst per 500 g. slurry liquid.Preferably about 5 to 50 g. dry catalyst per 500 g. slurry liquid slurryis utilized, being in about a respective 5:1 to 100:1 weight ratio.

The slurry system, comprised of the slurry liquid and finally dividedcatalyst, is generally stirred to promote good dispersion during thepretreatment in the process to avoid catalyst settling and to eliminatemass transport limitations between the gas and liquid phases.

In the process, the hydrogen and CO are used in a molar ratio in thegaseous feedstream in about a 10:1 to 1:10 molar ratio, preferably 3:1to 0.5:1, and particularly preferred 1:1 to 2:1 molar ratio.

The temperature used in the process of this invention will generally beat least about 250° C., i.e., 250°-300° C., preferably being 260° to280° C., and particularly preferred 240°-270° C. Higher temperatureranges can also be used but tend to lead to lighter products and moremethane, lower temperature ranges can also be used but tend to lead tolower activity and wax formation. The pressure useful in the process ofthis invention will range between about 50 to 400 psig and preferablyabout 70 to 225 psig. Higher pressures can also be used but tend to leadto waxy materials, particularly in combination with lower temperature.

The space velocity used in the process is generally about 100 to 20,000volumes of gaseous feedstream/per volume of dry catalyst in theslurry/per hour and is preferably in the range of about 1,000 to 15,000v/v/hr, more preferably 1,000-10,000 v/v/hr and still more preferably5,000 to 10,000. Higher space velocities can also be used but tend tolead to lower % CO conversion, and lower space velocities can also beused but tend to lead to more paraffinic products.

The percent CO conversion obtainable in the subject process, whileproviding substantial quantities of C₂ -C₂₀ olefins, ranges from about30 to 80 percent and usually about 50 to 60 percent for sufficient C₂-C₂₀ olefin production.

"Total hydrocarbons" produced in the process is related to theselectivity of percent CO conversion to hydrocarbons being thosehydrocarbons from C₁ to about C₄₀ inclusive. Total hydrocarbonselectivity is generally 0 to 70 percent and higher, of the total COconverted, and the remainder converted to CO₂.

The percent C₂ -C₂₀ hydrocarbons of the total hydrocarbons producedincluding methane and above is about 60 to 90 wt. %. The percent of C₂-C₂₀ olefins produced, of the C₂ -C₂₀ total hydrocarbons produced isabout 60 to 70 wt. %. The olefins produced in the process aresubstantially alpha olefins.

The selectivity to methane based on the amount of CO conversion is about1 to 10 weight percent of total hydrocarbons, produced. Preferably about5 percent, and lower, methane is produced in the process.

As discussed above, the percent selectivity to CO₂ formation in theprocess is about 10 to 50 percent of CO converted.

Preferably, the reaction process variables are adjusted to minimize CO₂production, minimize methane production, maximize percent CO conversion,and maximize percent C₂ -C₂₀ olefin selectivity, while achievingactivity maintenance in the catalyst system. In the laboratory, it isconvenient to use octacosane as the slurry liquid employing a catalystrepresented by the formula Fe₂.25 Mn₀.75 O₄ /1% Cu, 2% K and thecatalyst/liquid weight ratio of 7/500, while stirring the slurry at 600rpm. The conditions used in the laboratory both to activate the catalystin-situ in the slurry liquid and to conduct the Fischer-Tropschhydrocarbon synthesis process include an H₂ /CO molar ratio of 2:1, atemperature of about 270° C., a total pressure of 75 psig and spacevelocity of 1,000-12,000 v/v/hr. These conditions have been found toresult in efficient maintenance of the catalyst activity and C₂ -C₂₀olefin production.

The effluent gases in the process exiting from the reactor may berecycled if desired to the reactor for further CO hydrocarbon synthesis.

Methods for collecting the products in the process are known in the artand include fractional distillation, and the like. Methods for analyzingthe product liquid hydrocarbons and gaseous streams are also known inthe art and generally include gas chromatography, liquid chromatography,high pressure liquid chromatography and the like.

This invention will be more readily understood by reference to theexamples below.

EXAMPLES

Unless otherwise indicated, the selectivity weight percentages, based oncarbon, of product hydrocarbons is given on a CO₂ -free basis.

Catalyst Evaluation Under CSTR-Slurry Reactor Conditions

Into a slurry reactor, being a 300 cc Parr CSTR (continuous stirred tankreactor) was charged: 72 g of octacosane and 0.5-8.0 g. of the spinel orcatalyst being studied. The system was purged with nitrogen while thetemperature was increased from room temperature to 200° C. The systemwas then placed under CO hydrogenation reaction conditions by adjustingthe reaction temperature to 270° C., the H₂ /CO volume ratio to 2:1, thespace velocity to 1500-24,000 V gaseous feedstream/V dry catalyst/hr,the pressure to 75 psig, and the slurry stirrer speed to 600 rpm in theoctacosane solvent. The effluent gas from the reactor was monitored byan HP-5840A Refinery Gas Analyzer to determine percent CO conversion andthe nature of the hydrocarbon products.

EXAMPLE 1 Preparation and Evaluation of High Surface Area Fe₂.25 Mn₀.75O₄ Spinel

39.1 grams of ferric nitrate (Fe(NO₃)₃.9H₂ O) in 55 cc of water and 9.3grams of manganese nitrate Mn(NO₃)₂.6H₂ O in 10 cc of water were mixedtogether. A solution was prepared by adding to 11.5 grams of 85%glycolic acid a sufficient amount of ammonium hydroxide such that theresulting pH of the ammonium glycolate solution was about 6.5. Theammonium glycolate solution consituted 0.129 moles of glycolic acid suchthat about a one to one molar ratio of iron and manganese metal toglycolic acid resulted. The ammonium glycolate solution was added to theaqueous solution containing iron and manganese salts and the contentsstirred. The resulting solution was allowed to evaporate by air dryingat room temperature.

The resulting dry solid was shown by X-ray diffraction to be anamorphous material because of lack of sharp, discrete reflections. Thesolid was heated in air at 175° C. for two hours. An X-ray diffractionpattern of the resulting material showed it to be a single phase,manganese/iron spinel isomorphous with Fe₃ O₄. The X-ray diffractionpeaks were broadened relative to a compositionally equivalent materialobtained by a higher temperature procedure. This indicated that theresulting obtained material was of very small particle size. The surfacearea of the resulting material was about 100 square meters per gram.

The resulting material was then impregnated with (one or two) gramatomic percent of potassium using an aqueous solution of potassiumcarbonate and drying the resulting impregnated sample at 125° C. Theresulting solid had an empirical formula of Fe₂.25 Mn₀.75 O₄ /2%K. Forthe samples also containing the Cu promoter, 1 gm atom % of Cu, via anaqueous copper nitrate solution was impregnated onto the sample whichwas then dried at 125° C.

EFFECT OF CATALYST LOADING

A number of runs were made in the CSTR reactor with each run employing adifferent amount of catalyst which varied from 1 to 8 grams. The resultsare set forth in Table 1 below.

                  TABLE 1                                                         ______________________________________                                        CSTR PERFORMANCE OF Fe.sub.2.25 Mn.sub.0.75 O.sub.4 /2% K, 1% Cu              GMS Catalyst     1       2       4     8                                      ______________________________________                                        % CO Conversion  68.9    83.0    87.0  87.0                                   Wt % Selectivity                                                              (based on C.sub.1 + hydrocarbons)                                             CH.sub.4         1.7     2.3     2.8   4.1                                    % α-olefin in C.sub.2 -C.sub.4                                                           93.5    92.0    93.0  92.0                                   % α-olefin in C.sub.10                                                                   63.1    64.7    65.0  55.0                                   ______________________________________                                         Conditions: 270° C., 75 psi, H.sub.2 :CO:N.sub.2 SCCM = 120:60:20,     72 gm octacosane solvent, 30+ hr on feed.                                

The data in Table 1 above show the high α-olefin selectivity obtainedwith the catalyst of this invention when operated under slurry reactionconditions with less than 10% wt. catalyst loading. Due to its highintrinsic activity, this catalyst is able to convert large quantities ofH₂ /CO feed even at the relatively low catalyst loadings employed.

EXAMPLE 2 Effect of Promoter and Surface Area

The Fe₂.25 Mn₀.75 O₄ high surface area spinels were prepared followingthe procedure in Example 1.

For comparison purposes, low surface area (BET 0.21 M² /g) catalysts(Runs 4 and 5) were prepared according to the procedure set forth inExample 1 of copending U.S. application Ser. No. 564,464. Thus 17.293 g.of Fe₂ O₃, 1.5119 g. Fe and 6.1946 g. of Mn₃ O₄ were carefully weighed,thoroughly mixed and placed into a quartz tube (15 mm i.d., 18 mm o.d.)evacuated to 10⁻³ torr, sealed under vacuum and then heated to 800° C.for 24 hours. The resulting solids were isolated, thoroughly reground,pelletized and resubjected to the same high temperature sinteringprocess at 800°-1000° C. for an additional 24 to 48 hours. Powder X-raydiffraction analysis was then conducted to ensure that the material wassingle phase and isostructural with Fe₃ O₄. The catalyst pellets werethen impregnated with aqueous solutions of K₂ CO₃ to achieve a potassiumloading level of 2 gm atom percent K per gm atom of combined metal, andthen dried. For run 5, the powder was further impregnated with 1 gm atompercent Cu per gm atom of combined metal, and then dried.

Two grams of each spinel were loaded into the CSTR reactor with theresults set forth in Table 2 below.

                  TABLE 2                                                         ______________________________________                                        PERFORMANCE OF K AND K--CU                                                    PROMOTED Fe.sub.2.25 Mn.sub.0.75 O.sub.4 CATALYST                             Run               1      2      3    4    5                                   ______________________________________                                        % K               --     2.0    2.0  2.0  2.0                                 % Cu              1.0    --     1.0  --   1.0                                 Surface Area (M.sup.2 /gm)                                                                      >50    >50    >50  <5   <5                                  GMS Catalyst      2.0    2.0    1.0  2.0  2.0                                 % CO Conversion    34     36     69  Nil  Nil                                 Wt % Selectivity                                                              (based on C.sub.1 + hydrocarbon basis)                                        CH.sub.4          8.8    3.5    1.7  *    *                                   % α-olefin in C.sub.2 -C.sub.4                                                             78     91     94  *    *                                   % α-olefin in C.sub.10                                                                    *      *       63  *    *                                   ______________________________________                                         Conditions: 270° C., 75 psi, 120:60:20 SCCM H.sub.2 :CO:N.sub.2,       70-80 gms octacosane solvent, 20+ hr on stream.                               *insufficient quantities of product generated for meaningful analysis.   

The data in Table 2 show the superior slurry reactor behavior of thecatalyst of this invention (Run 3) compared to both the relatively lowsurface area Fe-Mn catalysts (Run 4 and 5) and the high surface areaspinel catalyst with only Cu (Run 1) or K (Run 2) promoters present.These data also show that with Cu and K promoters, the amount of COconversion was nearly four times that obtained with the high surfacearea catalyst promoted with Cu or K only.

EXAMPLE 3 Effect of Fe:Mn Ratio

Four high surface area Cu and K promoted spinels were made following theprocedure set forth in Example 1. One spinel had the composition setforth in Example 1 whereas the Fe:Mn ratio of the other two spinels waschanged by varying the relative amounts of the ferric and manganesenitrate reagents. Two grams of each spinel were then loaded into theCSTR reactor, with the results listed in Tables 3 and 4 below.

                  TABLE 3                                                         ______________________________________                                        CSTR PERFORMANCE AS A FUNCTION OF Fe:Mn RATIO                                 ______________________________________                                        Fe.sub.3-x Mn.sub.x O.sub.4 /2% K, 1% Cu                                      (>50 M.sup.2 /g spinels)                                                      X =                0.75     1.5    2.75                                       % CO Conversion    83       30     Nil                                        Wt % Selectivity                                                              (based on C.sub.1 + hydrocarbons)                                             CH.sub.4           2.3      2.6    NA                                         % α-olefin in C.sub.2 -C.sub.4                                                             93       86     NA                                         ______________________________________                                         Conditions: 2.0 gms catalyst, 270° C., 75 psig, 120:60:20 SCCM         H.sub.2 :CO:N.sub.2, 72 gms octacosane solvent, 30+ hr on stream.        

The data in Table 3 demonstrate the good activity and α-olefinselectivity obtained with the catalyst of the present inventioncontaining Mn up to the Mn:Fe ratio of 1:3 i.e. x=0.75. In contrast, anidentical catalyst containing higher levels of Mn where Mn:Fe=1:1 or11:1, i.e. x=1.5 or 2.75, exhibited substantially lower activity underthe indicated slurry reactor conditions.

                  TABLE 4                                                         ______________________________________                                        CSTR PERFORMANCE AS A FUNCTION OF Fe:Mn Ratio                                 ______________________________________                                        Fe.sub.3-x Mn.sub.x O.sub.4 /2% K, 1% Cu                                      (>50 M.sup.2 /g spinels)                                                      X =                   0.15   0.75                                             % CO Conversion       79     87                                               Wt % Selectivity                                                              (Based on C.sub.1 + hydrocarbons)                                             CH.sub.4              4.2    4.1                                              % Olefin in C.sub.2 -C.sub.4                                                                        94     92                                               ______________________________________                                         Conditions: 8 gms catalyst, 270° C., 75 psig, 120:60:20 SCCM           H.sub.2 :CO:N.sub.2, 72 gms octacosane solvent, 30+ hr on stream.        

The data in Table 4 demonstrate the high activity and α-olefinselectivity of the catalyst of the present invention when the Fe/Mnratio is maintained in the range 3/1 to 19:1.

EXAMPLE 4

In this example, the CSTR performance of two high surface area glycolatederived spinels prepared according to the procedure set forth in Example1 were compared to a potassium promoted, precipitated Fe-Mn oxideprepared according to the procedure of Kolbel in U.S. Pat. No. 4,177,203and H. Schulz, Proceedings 8th Int. Congress on Catalysis, II, P.123-133 (1985). Thus an aqueous solution of 57.5 g of Mn(NO₃)₂.6H₂ O in100 cc of H₂ O was added to a solution of 7.23 g of Fe(NO₃)₃.9H₂ Odissolved in 10 cc of H₂ O. The combined solutions were heated to 80° C.and about 100 cc of NH₄ OH was added to form a precipitate which wasfiltered and dried in air overnight at 110° C. Four g of the resultingpowder was impregnated with 2 cc of a solution prepared by dissolving0.85 g K₂ CO₃ in 100 cc H₂ O and dried.

The results are set forth in Table 5.

                  TABLE 5                                                         ______________________________________                                        RELATIVE PERFORMANCE OF GLYCOLATE                                             DERIVED SPINELS AND PRECIPITATED,                                             LOW Fe--Mn RATIO CATALYSTS                                                                   2% K, 1% Cu                                                                              0.5% K                                                             Promoted   Promoted,                                                          Glycolate  Precipitated                                                       Derived                                                                              Spinel  Fe--Mn                                          ______________________________________                                        Fe:Mn            3:1      1:11    1:11                                        % CO Conversion  83       Nil     Nil                                         Wt % Selectivity                                                              (based on C.sub.1 + hydrocarbons)                                             CH.sub.4         1.9      *       *                                           % α-olefin in C.sub.2 -C.sub.4                                                           93       *       *                                           ______________________________________                                         Conditions: 2 gms catalyst, 270° C., 75 psig, 120:60:20 SCCM           H.sub.2 :CO:N.sub.2, 72 gms octacosane, 20+ hr on stream.                     *Insufficient quantities of product generated meaningful analysis.       

The data in Table 5 demonstrate the superior performance of the catalystof the present invention relative to a catalyst prepared by the methoddescribed in U.S. Pat. No. 4,177,203, etc. which was inactive in theslurry process. In addition, the catalyst prepared by the method of thepresent invention but containing Mn outside of the prescribed range,i.e. Fe:Mn=1:11 is found to be inactive under the low pressure slurryconditions employed.

EXAMPLE 5

In this example, the CSTR performance of a high surface area Cu and Kpromoted spinel of this invention was compared to a precipitated Fe-Mnoxide prepared according to the procedure set forth by Maiti et al.Thus, a catalyst was prepared by the procedure described by Maiti et al(Appl. Cat. 16(2), 215 (1985) in the Fe/Mn range where he observed hismost olefinic products: 98.8 of Fe(NO₃)₃.9H₂ O and 2.2 gm Mn(NO₃)₂.6H₂ Owere dissolved in 140 and 4 cc of H₂ O respectively and mixed to form asingle solution. A 10 wt% NH₄ OH solution was added to bring the pH ofthe nitrate solution to 6.4. This solution was then heated to 70° C.This nitrate solution and the NH₄ OH solution were placed in twoseparatory funnels and while stirring constantly, each solution wasadded dropwise into a single mixing vessel maintaining the pH of thesolution between 9.2 and 9.6 while the precipitate formed. Theprecipitate was filtered, and washed several times with H₂ O, dried at120° C. and finally calcined at 500° C.

The Maiti catalyst was charged into a CSTR reactor.

                  TABLE 6                                                         ______________________________________                                        RELATIVE PERFORMANCE OF GLYCOLATE                                             DERIVED SPINELS AND PRECIPITATED,                                             HIGH Fe/Mn RATIO CATALYSTS                                                              Glycolated Derived                                                                           Precipitated                                                   Spinel, K, Cu Promoted                                                                       Prep.                                                ______________________________________                                        Fe/Mn       19:1             32                                               WT catalyst (gm)                                                                          1                2                                                % CO conversion                                                                           68.9             20.5                                             CH.sub.4    1.7              7.4                                              % α-olefin, C.sub.2 -C.sub.4                                                        93.5             87.2                                             ______________________________________                                         The results show the higher activity, olefinuity and lower methane            selectivity with the catalyst of this invention vs. the preparation           described in Appl. Cat. 16(2), 215 (1985).                               

EXAMPLE 6

In this Example, the CSTR performance of a high surface area Cu and Kpromoted spinel of this invention was compared to a precipitated andsintered Fe-Mn composition prepared according to the procedure set forthin U.S. Pat. No. 2,778,845.

An Fe/Mn catalyst was prepared as described by McGrath et al (U.S. Pat.No. 2,778,845). Thus, 10 gm of Mn(NO₃)₂.6H₂ O was dissolved in 2 cc ofH₂ O by heating to 80° C. This was mixed with 54 gm of Fe₃ O₄, theanalog of Alan Wood magnetite. The paste which formed was driedovernight at 90° C. 0.35 gm of K₂ CO₃ in 4 cc H₂ O was heated to 90° C.and mixed with the material dried above. An additional 2.5 cc of H₂ Owas added to thoroughly mix the K₂ CO₃ solution and the dried paste.This was then dried at 90° C. for several hours. This mix was heated to1400° C. for 6 hours and cooled. The solidified chunk was ground andheated in a 20% H₂ /80% He stream (at 500 cc/min total flow) at 371° C.for 48 hours. The catalyst was gently passivated at room temperaturewith a 1% O₂ /99% He stream. 2 gms catalyst was loaded in 72 gm ofoctacocane. The results are shown in Table 7.

                  TABLE 7                                                         ______________________________________                                        RELATIVE PERFORMANCE OF GLYCOLATE DERIVED                                     SPINELS AND HIGH TEMPERATURE Fe/Mn CATALYSTS                                           Glycolated Derived Spinels                                                                     Precipitated                                                 Promoted With 2% K, 1% Cu                                                                      Prep.                                               ______________________________________                                        Fe:Mn      3:1                7:1                                             % CO conversion                                                                          83                 Nil                                             Wt. % Selectivity                                                             (Based on C.sub.1 +                                                           hydrocarbons)                                                                 CH.sub.4   1.9                *                                               % α-olefin, C.sub.2 -C.sub.4                                                       93                 *                                               ______________________________________                                         Conditions: 2 gms catalyst, 270°C., 75 psig, 120:60:20 SCCM H.sub.     :CO:N.sub.2, 72 gms octacosane, 20+ hr on stream.                             *Insufficient quantities of product generated for meaningful analysis.   

The data in Table 7 demonstrates the superior performance of thecatalyst of the present invention relative to a catalyst prepared by themethod described in U.S. Pat. No. 2,778,845, which was inactive in theslurry process.

What is claimed is:
 1. A composition of matter comprising anunsupported, Group IA or IIA metal and copper promoted, single phase,iron-manganese spinel, said spinel exhibiting a powder X-ray diffractionpattern substantially isostructural with Fe₃ O₄, and possessing a BETsurface area greater than 30 M² /g and an iron-manganese atomic ratiogreater than about 2:1.
 2. The composition of matter of claim 1 whereinsaid promotor metals are deposited substantially on the surface of saidspinel.
 3. The composition of matter of claim 2 wherein said surfacearea is at least about 50 M² /g.
 4. The composition of matter of any ofclaims 1, 2 or 3 wherein said spinel is of the formula: Fe_(x) Mn_(y)O₄, wherein x and y are integer or decimal values, other than zero, andwherein the sum of x+y is 3, and the ratio of x/y is at least about 2:1.5. The composition of matter of claim 4 wherein the ratio of x/y is inthe range of from about 2:1-19:1.
 6. The composition of matter of claim5 wherein the ratio of x/y is about 3:1 to 7:1.
 7. The composition ofmatter of claim 1 further comprising a mixture of said spinels in whichat least two iron-manganese spinels are present, being isostructuralwith Fe₃ O₄, each having BET surface areas greater than 30 M² /g,wherein said spinels individually possess different iron-manganeseatomic ratios, which are at least 2:1.
 8. The composition of matter ofclaim 1, 2 or 3 wherein said copper promoter is present in an amount offrom about 0.1 to 10 gram-atom percent of metal ion based on the totalgram-atoms of iron-manganese metals content.
 9. The composition ofmatter of claim 2 wherein said copper promoter is present in an amountof from about 0.5 to 2 gram atom % of the iron-manganese metals content.10. The composition of matter of claim 8 wherein said Group IA or IIApromoter metal is present in an amount of from about 0.1 to 10 gram-atom% of the total metals gram-atom of said composition.
 11. The compositionof any of claims 1, 2 or 7 wherein said composition is in itsreduced-carbided form.
 12. The composition of claim 4 wherein saidcomposition is in its reduced-carbided form.
 13. A process for producinga composition of matter comprising an unsupported, single phase, GroupIA or IIA metal and copper promoted iron-manganese spinel, said spinelexhibiting a powder X-ray diffraction pattern substantiallyisostructural with Fe₃ O₄, and possessing a BET surface area greaterthan 30 M² /g and an iron-manganese atomic ratio greater than about 2:1comprising the steps of (a) evaporating a liquid solution comprising amixture of iron and manganese salts of at least one alpha-hydroxyaliphatic carboxylic acid, wherein the molar ratio of total moles ofsaid acid to total moles of said iron and manganese, taken as freemetals, is about 1:1, or above, and wherein the atomic ratio ofiron:manganese, taken as the free metals in said mixture, is greaterthan 2 to 1, yielding an amorphous residue; (b) calcining said residueat elevated temperature for a time sufficient to yield an iron-manganesespinel, exhibiting only one spinel phase, isostructural with Fe₃ O₄, asdetermined by powder X-ray diffractometry; (c) impregnating thecomposition of (b) with a solution of a copper salt and a salt of aGroup IA or IIA metal; and (d) drying the resulting impregnate.
 14. Theprocess of claim 13 wherein said acid is selected from glycolic, malic,tartaric, or lactic acids, or mixtures thereof.
 15. The process of claim14 wherein said solution is an aqueous solution.
 16. A composition ofmatter comprising, a single phase, copper and Group IA or IIA metalpromoted iron-manganese spinel produced by a process comprising thesteps of (a) evaporating a liquid solution comprising a mixture of ironand manganese salts of at least one alpha-hydroxy aliphatic carboxylicacid, wherein the molar ratio of total moles of said acid to total molesof said iron and manganese, taken as free metals, is about 1:1, orabove, and wherein the atomic ratio of iron:manganese, taken as the freemetals in said mixture, is greater than 2 to 1, yielding an amorphousresidue; (b) calcining said residue at elevated temperature for a timesufficient to yield a spinel; (c) impregnating the composition of (b)with a solution of a copper salt and a salt of a Group IA or IIA metal;and (d) drying the resulting impregnate.